Neurosurgery routinely involves performing craniotomies for exposure of the brain and intracranial contents for various intracranial pathologies including tumors, head injuries, vascular malformations, aneurysms, infections, hemorrhages, strokes, and brain swelling. A craniotomy involves creation of burr holes and removal of a portion of the skull (bone flap) with subsequent approximation of the bone flap for closure. Several methods and fixation devices are available for re-attaching the bone flap to the skull including small metallic or absorbable plates with screws or wires as demonstrated in U.S. Pat. No. 5,578,036 to Stone et al., U.S. Pat. No. 5,916,200 to Eppley et al, and U.S. Pat. No. 5,916,217 to Manthrop et al. Another method has been the use of cranial clamps consisting of two connected circular elements placed on the inside and outside surfaces of the skull.
Cranial clamps are superior to the plates because they are faster to place and do not involve additional drilling of screw holes or downward pressure onto the skull with a screwdriver. Various descriptions of cranial clamps in the art include U.S. Pat. No. 5,707,373 to Sevrain, U.S. Pat. No. 5,800,436 to Lerch, U.S. Pat. No. 6,485,493 to Bremer, U.S. Pat. No. 6,379,363 to Herrington et al., U.S. Pat. No. 6,755,834 to Amis, U.S. Pat. No. 7,048,737 to Wellisz et al., U.S. Pat. No. 7,361,178 to Hearn et al., U.S. Pat. No. 7,387,633 to Ahmad et al., and U.S. Pat. No. 6,685,707 to Roman et al. In U.S. Pat. No. 6,589,244, Sevrain et al. describe a cranial clamp with caps that have studs that lock into a fixed position by screwing into each other.
Unfortunately, placement of these cranial clamps as described in the prior art requires additional devices which further complicates and prolongs the procedure. In general, all of the clamps essentially consist of two circular elements connected by a rod or a shank whereby the circular elements can be moved relative to one another to adjust to the thickness of the bone and fixate the bone flap to the skull. Subsequent to the fixation, the remaining rod is cut off and the clamps are permanently fixed in that position. Their remain several drawbacks to this methodology making the cranial clamps difficult to use and prolong the procedure by requiring an instrument to compress the circular elements together against the bone and once positioned, the need for another instrument for cutting the remaining rod off. Another drawback includes application of excessive force by squeezing the two clamps together against the skull and bone flap. Yet another drawback includes the significant effort required to remove the clamps locked in place in cases of re-operation.
Thus, there is a need for improved cranial fixation devices that allow fast and easier fixation of the bone flap to the skull along with greater ease of removal during a re-operation.